1. Field of the Invention
The present invention relates to plastic welding and molding apparatus and, more particularly, to radio frequency (RF) heated thin wall molds for applying RF energy to heating, welding, or molding plastic elements.
2. Description of Related Art
Thermoforming of plastic material is well known and has been employed to develop tip welds in plastic tubing used for catheters. Similarly, assembly welds, such as butt welds and annular welds of plastic tubing or other plastic elements can be done by a thermowelding process.
Apparatus for effecting thermoforming may include mechanical heating elements which perform a thermoforming function primarily by heat transfer through conduction. Commensurately or in the alternative, heat transfer by radiation has been used. The presently most widely used apparatus for thermoforming constitutes the use of electrically energized inductive heating devices. Such devices are capable of performing high quality welds but suffer from several drawbacks. First, the power requirements are relatively substantial. Second, it is essentially impossible to monitor with any precision the temperature of the tubing being welded; the power applied is primarily a function of the skill of the operator based upon experience. Third, due to the relatively large mass of the apparatus, the thermal inertia is substantial, which delays both heating and cooling thereby extending production cycle time.